Private speech refers to speech uttered out loud by children which is addressed to the self. According to Vygotsky (1962), it serves the developmental function of bringing action under verbal control; with increasing cognitive maturity it is internalized as verbal thought. Though based upon Vygotsky's ideas, programs providing training in verbal self-regulation for children with learning problems have not shown improvements in problem-solving and academic performance. One reason may be that they are not grounded in research that definitively verifies Vygotsky's theory. From previous studies it is unclear whether private speech is a product of task demands (e.g., task difficulty and time constraints), intellectural maturity, or both factors. The proposed research will disentangle these variables in investigating Vygotskian predictions. In addition, the role of private speech in facilitating attention and task performance will be studied. The research will be carried out in three parts. Study 1 uses data on 1981 children from the Kaufman Assessment Battery for Children (KABC) standardization sample to derive estimates of task difficulty, based on age and intellectual ability, for 15 items on the KABC Photo Series Subtest. These estimates are used in Studies 2 and 3 to test the major research hypotheses. In Study 2, 100 children from 4 to 8 years of age and of two levels of intellectual ability (average and bright) will be administered Photo Series items of average and high difficulty (with task difficulty adjusted for each child's age and intellectual ability). Private speech, attention to task, and task performance will be recorded on videotape. In Study 3, the same design and methodology will be repeated, but an additional task constraint will be introduced--time limitations for task completion. The videotapes will permit exploration of two additional Vygotskian theoretical issues: (a) developmental changes in the temporal relationship between private speech and task-related behaviors; and (b) microgenetic, within-subjects changes in children's use of private speech. The combination of both broad and microgenetic developmental information should contribute to a fuller understanding of the functional significance of private speech and serve as useful data for the design of interventions to help ineffective and less mature learners acquire more successful strategies.